The present invention relates to a positive-working light-sensitive composition which permits the formation of a lithographic printing plate, a multicolor proof sheet and a figure for use in an overhead projector as well as fine resist patterns when producing integrated circuits of semiconductors.
Ortho-quinonediadide compounds have conventionally been known as so-called positive-working light-sensitive substances for use in making, for instance, lithographic printing plates and are solubilized through irradiation with actinic light rays and in fact, they have widely been used for the preparation of lithographic printing plates. Such o-quinonediazide compounds are disclosed in various publications such as U.S. Pat. Nos. 2,766,118; 2,767,092; 2,772,972; 2,859,112; 2,907,665; 3,046,110; 3,046,111; 3,046,115; 3,046,118; 3,046,119; 3,046,120; 3,046,121; 3,046,122; 3,046,123; 3,061,430; 3,102,809; 3,106,465; 3,635,709; and 3,647,443.
These o-quinonediazide compounds can be decomposed through irradiation with actinic light rays to give 5-membered cyclic carboxylic acids and thus are made alkali-soluble. The positive-working light-sensitive composition makes use of the foregoing properties of these compounds, but the sensitivity thereof is still insufficient. This is because it is difficult to photochemically sensitize these o-quinonediazide compounds and correspondingly, the quantum yield thereof does not essentially exceed 1.
Moreover, lithographic printing plates or the like are in general prepared by imagewise exposing, to light, presensitized plates comprising light-sensitive layers containing these compounds using a printer to form desired patterns and then removing the exposed areas thereof with an alkali developer or a solvent. However, the presensitized plate suffers from various problems. For instance, the sensitivity of the presensitized plate is changed (narrow development latitude) since the development thereof is greatly affected by various factors such as temperatures and concentrations of developers and solvents used and developing time.
Moreover, the light-sensitive materials comprising o-quinonediazide compounds are sensitive only to light rays of specific wavelengths, light sources usable for the development thereof are accordingly limited to specific ones and this makes it difficult to impart stability to white light to the light-sensitive materials. In addition, the compounds have high absorbances in the Deep UV region and therefore, they cannot favorably be applied to, for instance, photoresists which require the improvement in the resolving power through the use of light rays of short wavelengths.
Many attempts have been done for the elimination of these disadvantages, for instance, methods disclosed in various publications such as Japanese Patent Publication for Opposition Purpose (hereunder referred to as "J.P. KOKOKU") No. Sho 48-12242, Japanese Un-examined Patent Publication (hereunder referred to as "J.P. KOKAI") No. Sho 52-40125 and U.S. Pat. No. 4,307,173, but there has still remained a room for improvement.
Recently, some attempts have been proposed for the development of novel positive-working light-sensitive materials which can be used in place of the o-quinonediazide compounds. For instance, J.P. KOKOKU No. Sho 56-2696 discloses polymeric compounds having o-carbinol ester groups. However, these novel positive-working light-sensitive materials were still insufficient in sensitivity.
On the other hand, methods for forming patterns while making use of photoresists have generally been adopted in the production of electronic parts such as semiconductor elements, magnetic bubble memories and integrated circuits. In addition, a high packaging density and a high level of integration have increasingly been required for the production of electronic parts such as semiconductor elements and correspondingly, there has been required for the formation of patterns of very fine line widths and line spaces and the dry etching method has been adopted for etching substrates. For this reason, there has been desired for the development of photoresists exhibiting high resolving power and high resistance to dry etching and accordingly, negative-working photoresists currently used exclusively have been superseded by positive-working photoresists recently. In particular, there have widely been used currently alkali-developable positive-working photoresists mainly comprising alkali-soluble novolak resins such as those disclosed in, for instance, J. C. Striata, Kodak Microelectronics Seminar Proceedings, p. 116 (1976) because of their high sensitivity, high resolving power and excellent resistance to dry etching.
However, there has intensively been required for the formation of finer patterns in order to further increase the packaging density and the level of integration of electronic machinery and equipments in proportion to the recent increase in the diversity and required sensitivity thereof. To meet these demands, there have been proposed light-sensitive materials comprising the combinations of the conventional o-quinonediazide light-sensitive substances with silicone polymers such as polysiloxanes or polysil methylenes which are made alkali-soluble such as light-sensitive compositions disclosed in, for instance, J.P. KOKAI Nos. Sho 61-256347, Sho 61-144639, Sho 62-159141, sho 62-191849, Sho 62-220949, Sho 62-229136, Sho 63-90534 and Sho 63-91654; and light-sensitive compositions comprising combinations of polysiloxane/carbonate block copolymers with effective amounts of onium salts such as those disclosed in, for instance, J.P. KOKAI No. Sho 62-136638. However, these silicone polymers should be converted into alkali-soluble ones and this makes the preparation thereof very difficult. Moreover, they are insufficient in stability with time.
An example of the positive-working light-sensitive material which has recently been proposed and which is usable instead of the conventional quinonediazide compound includes a composition comprising a compound capable of photolytically generating an acid, a compound whose solubility in an alkaline water can be changed through, for instance, hydrolysis with an acid and an optional binder resin. There may be mentioned, for instance, a method for forming a positive image by decomposing a specific low molecular weight or high molecular weight acetal and O,N-acetal comprising an aromatic compound as a hydroxyl or amine component (U.S. Pat. No. 3,779,778), and an ortho ester and an amidoacetal (DEOS No. 2,610,842) with an acid generated through exposure to light. Moreover, methods for forming positive images in the same manner are disclosed in, for instance, J.P. KOKAI Nos. Sho 64-33546, Sho 48-89003, Sho 51-120714, Sho 53-133429, Sho 55-126236, Sho 53-133428, Sho 55-12995, Sho 57-31674, Sho 57-31675, Sho 57-37347, Sho 62-215947, Hei 1-106040 and Hei 1-106041.
However, all of these conventional compositions have low sensitivity or a low solubility difference between exposed and non-exposed areas or provide only insufficient shapes of patterns of the resulting positive images and therefore, they have not yet been practically used.
Further J.P. KOKAI No. Sho 62-45971 discloses that a positive image can be formed in the same manner described above through the use of an enol ether group-containing compound as a compound capable of being decomposed with an acid. In addition, J.P. KOKAI No. Hei 4-215661 discloses that a positive image can be formed in the same manner discussed above by reacting a monofunctional vinyl ether compound with carboxyl groups present on a resin to form a polymer having an acetal structure. However, these methods provide clear positive images only under limited image-forming conditions because of low sensitivity and a low solubility difference between exposed and non-exposed areas.